It's painful to see a book that could have been a quality product suffer due to sloppy mistakes. But that's a major problem with this book. (Unlikeable characters that are criminally stupid, selfish, entitled, immature or some combination of at least two of those things make for another issue. But that's for later.) Despite the fact that Gillam's voice was clearly defined and the mystery well-developed (or, developed well enough), consistency and (major) continuity errors, grammar slip-ups, and other little things greatly detract from the story. I was amazed that Gillam was able to maintain the literary suspense when the more glaring errors (such as a police vehicle from a cash-strapped department exploding one night, but only requiring a tow and a quick look-see from the local mechanic the next day) suspended my own suspension of disbelief time and time again. In fact, the author's ability not to ruin the mystery has a lot to do with why this is a 2.5-star book instead of a zero- or 1-star book; that, among other things, shows she's super talented.
The characters are another story altogether. But I'll have to save my issues with for an edit. There will be spoilers that need better hiding than I can manage from a tablet.